The invention relates to a burner for generating a flame by combustion of a fuel, comprising: a tile surrounding an opening of the tile extending along a burner axis, the tile further comprising a front side and a rear side facing away from the front side, wherein the rear side comprises an air inlet connected to said opening for feeding air into said opening, and wherein said front side comprises a discharge outlet connected to said opening for discharging a flame generated by the burner into a surrounding area, and wherein the tile further comprises an inside facing said opening as well as an outside facing away from said opening, the burner further comprising at least one oxygen lance extending along the burner axis in a first recess of said tile, the at least one oxygen lance having an ejection nozzle at an end region of the at least one oxygen lance for ejecting oxygen, characterized in that the first recess for receiving the at least one oxygen lance is formed as a slot formed in the outside of the tile as well as to a method for generating a flame using such a burner.
Such a burner, particularly a Low-NOX-burner, for generating a flame by combustion of a fuel usually comprises a first (e.g. circumferentially extending) refractory tile surrounding an e.g. central opening of the tile, which opening extends along a burner axis, wherein the tile further comprises a front side and a rear side that faces away from said front side, and wherein the rear side comprises an air inlet in flow connection to said opening for feeding air into said opening, and wherein said front side comprises a discharge outlet being in flow connection to said opening for discharging a flame generated by the burner into an ambient surrounding, particularly into a firebox (e.g. of a furnace). Further, the tile comprises an inside facing said opening as well as an outside facing away from said opening/inside.
These burners are for instance used in the oil industry and are e.g. designed according to API RP535 (“Burners for Fired Heaters in General Refinery Services”, API recommended practice 535, second edition, January 2006). Particularly, these Low-NOx-burners are either fuel or air staged to manage the peak flame temperature reducing the thermal NOx.
The generation of nitrogen oxides (NOx) can have different origins in the combustion process conducted in a burner of the afore-mentioned kind.
At first, NOx may be produced from N2 in the so-called prompt or immediate conversion wherein NOx is produced from N2 within the early stages of the combustion process through a hydrocarbon radical-mechanism, i.e., N2 reacts with radicals such as C, CH, and CH2 fragments derived from the fuel. In the early stages of combustion this results in the formation of fixed species of Nitrogen such as NH, HCN, H2CN and cyano (CN—) radicals which may oxidize to NO.
Further, in the so-called thermal conversion being the temperature dependent oxidation of N2 to NOx, which is favored by high temperatures, the following reactions producing NOx may occur according to the extended Zeldovich mechanism:N2+O→NO+NN+O2→NO+O, andN+OH→NO+H.
Finally, also a so-called fuel bound nitrogen conversion occurs, where nitrogen compounds within the fuel are converted to NOx. Here, during combustion, nitrogen bound in the fuel may be released as a free radical and may ultimately form N2 or NO.
Thus, the thermal NOx production is limited by reducing the flame temperature. This will reduce the NOx formed, since the corresponding reactions are favored by high temperatures. Fuel NOx is a function of fuel composition. The higher the chemically bound nitrogen in the fuel, the higher the NOx emissions might be. Finally, prompt NOx usually only produces a small amount of the generated NOx, which however may be a significant portion of the total NOx when a low-NOx-burner is employed that reduces the total NOx.
Based on this prior art, the problem underlying the present invention is to provide for an improved burner that is capable of producing less NOx and a corresponding method for generating a flame using such a burner.